In-medium effects of nucleon-nucleon cross sections in heavy-ion collisions

Abstract

Based on the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model, we systematically investigate the in-medium effects of nucleon-nucleon ($NN$) cross sections on nucleonic and pionic observables in heavy-ion collisions, employing microscopic cross sections derived from the Brueckner-Hartree-Fock approach. Key observables include nuclear stopping, the neutron-to-proton ($n/p$) ratio, neutron-proton transverse flow differences, differential collective flow, pion multiplicities, and the resulting $({\pi }^{-}/{\pi }^{+}{)}_{\mathrm{like}}$ ratio. The analysis disentangles the respective contributions from the scattering amplitude, the density of states, and the total momentum ($K$) of the colliding pairs. We find that larger in-medium $NN$ cross sections generally enhance free nucleon emission and nuclear stopping, with the nucleon effective mass playing a dominant suppressive role. However, it is insufficient to account only for the medium corrections from effective mass: both the medium effect from the scattering amplitude and the $K$-dependence exert noticeable influences on the observables. In particular, nuclear stopping is found to be highly sensitive to these in-medium modifications of cross sections. While the $n/p$ ratio and transverse flow difference remain largely insensitive, the differential collective flow and pion yields are strongly affected. These results indicate that the interplay between scattering amplitude, density-of-states and $K$-dependence is essential to accurately describe medium effects in heavy-ion collisions.

arXiv comment11 pages, 9 figures, version accepted for publication in Phys. Rev. C (2026)

References in corpus (40)

• Recent Progress and New Challenges in Isospin Physics with Heavy-Ion Reactions
• Circumstantial evidence for a soft nuclear symmetry energy at supra-saturation densities
• Nucleon-nucleon cross sections in neutron-rich matter and isospin transport in heavy-ion reactions at intermediate energies
• Probing the High Density Behaviour of Nuclear Symmetry Energy with High Energy Heavy-Ion Collisions
• Microscopic Calculation of in-Medium Nucleon-Nucleon Cross Ssections
• Neutron-Proton Differential Flow as a Probe of Isospin-Dependence of Nuclear Equation of State
• Microscopic Calculation of in-Medium Proton-Proton Cross Sections
• Understanding transport simulations of heavy-ion collisions at 100 and 400 AMeV: Comparison of heavy ion transport codes under controlled conditions
• Comparison of heavy-ion transport simulations: Collision integral in a box
• Near-threshold pion production with radioactive beams at the Rare Isotope Accelerator
• Systematics of Stopping and Flow in Au+Au Collisions
• Off shell behaviour of the in medium nucleon-nucleon cross section
• Probing the density dependence of the symmetry potential at low and high densities
• In-medium NN cross sections determined from stopping and collective flow in intermediate-energy heavy-ion collisions
• Comparison of Heavy-Ion Transport Simulations: Mean-field Dynamics in a Box
• The Disappearance of Flow
• Neutron-proton elliptic flow difference as a probe for the high density dependence of the symmetry energy
• Symmetry energy investigation with pion production from Sn+Sn systems
• Single and double pi^{-}/pi^{+} ratios in heavy-ion reactions as probes of the high-density behavior of the nuclear symmetry energy
• Determination of the nuclear incompressibility from the rapidity-dependent elliptic flow in heavy-ion collisions at beam energies 0.4\emph{A} - 1.0\emph{A} GeV
• Constraining the high-density nuclear symmetry energy with the transverse-momentum dependent elliptic flow
• Energy dependence of pion in-medium effects on π^-/π^+ ratio in heavy-ion collisions
• More on nucleon-nucleon cross sections in symmetric and asymmetric matter
• Double neutron-proton differential transverse flow as a probe for the high-density behavior of the nuclear symmetry energy
• Nucleon effective mass in hot dense matter
• The neutron/proton ratio of squeezed-out nucleons and the high density behavior of the nuclear symmetry energy
• Transport coefficients of nuclear matter in neutron star cores
• Accessing the in-medium effects on nucleon-nucleon elastic cross section with collective flows and nuclear stopping
• Modeling pion production in heavy-ion collisions at intermediate energies
• Nucleon momentum distributions in asymmetric nuclear matter
• Exact solution of the Brueckner-Bethe-Goldstone equation with three-body forces in nuclear matter
• Model dependence of isospin sensitive observables at high densities
• Effects of nuclear symmetry energy and in-medium NN cross section in heavy-ion collisions at beam energies below the pion production threshold
• Constraining nucleon effective masses with flow and stopping observables from the S$\pi$RIT experiment
• Probing the density dependence of the symmetry energy by nucleon flow
• Effects of incompressibility $K_0$ in heavy-ion collisions at intermediate energies
• Nucleon momentum gap in asymmetric nuclear matter
• Pion production and absorption in heavy-ion collisions
• Neutron-proton differential transverse flow in ${}^{132}$Sn + ${}^{124}$Sn collisions at 270 MeV/nucleon
• Probing in-medium nucleon-nucleon inelastic scattering cross section by using energetic n/p ratio